My watter bottle battery life is not what it used to be. So I'd like to replace it. The one from Jet Lights seems to be out of stock:

13v 3800mah NiMH Battery - JET Lites

Would it be possible to get another similar 13.2V battery like this one:

Water Bottle Nimh Battery: 13.2 V 5Ah (66 Wh) with Trail-Tech Female plug for HID / Halogen Bikelight

and modify the connector worse case? Would probably take the entire wire from the existing battery and solder and wrap the wires to the new one. Has anyone done this?

For that kind of money you could replace the whole setup with several sets of lights, why not upgrade?

Yeah, I was thinking of the same thing. Will have to look at some other alternatives. Jet Lights are nice but are pretty expensive. The older halogen light I have is really nice. However a newer LED should give similar performance and use less battery. Will see what's out there. This article talks about the Cygolite Dash 320 being a good bang for buck:

https://thesweethome.com/reviews/best...r-bike-lights/

I like the Light & Motion Urban 350 a little better though.